We were on a 03:20 Ferry out of Dover on Saturday for Spa, so went through Passport Control at around 02:30. No one there at all, no UK, and no French (as always).
The trips from Calais have been slow going getting through UK Passport Control for some years now, but it saves having to do it when you get back of course. When coming back on the Western Channel they don't do the UK stuff in France so you get to queue in France to checkin and then again back in the UK for Passport Control, so it's swings and roundabouts, in the end you have to queue somewhere!